This invention relates to a lock, particularly to one having a light weight, great strength, excellent anti-burglar and anti-strike feature, and low cost, with its pin tumbler locking mechanism well protected.
A conventional lock shown in FIG. 1 includes a U-shaped case 10 having a chamber 11, a locking member 12 contained in the chamber 11, a deadbolt 13 connected to an end of the locking member 12 and to be moved by the locking member to insert in a hole provided in the other end of the case 10, locking the lock.
FIGS. 2A and 2B respectively show the conventional lock in the locked and the unlocked position. The locking member 12 usually has a cylinder 121 rotatable, a number of pin tumblers 123 of different length and elastically and respectively pushed by the same number of springs 122, and the pin tumblers 123 obstructing a contacting line 124 formed between the locking member 12 and the cylinder 121 in case of the lock being in the locked position. If a correct key 125 is inserted in a key hole in the cylinder 121, the pin tumblers 123 are moved, not obstructing the separating line 124 permitting the cylinder 121 rotated to unlock the lock.
However, the conventional lock has an disadvantage of inferior anti-burglar function and weak structure caused by the feeble deadbolt 13 and the weak case 10.
Moreover, the convention lock has its pin tumblers 123 always protruding in an empty key hole in case of the lock locked so that the lock may be easily pried open or broken open by burglars. In addition, the pin tumblers 123 may be liable to wear off by frequent friction with the key 125, with accuracy between the key 125 and the pin tumblers 123 hard to maintain.